Time Machine backup on Synology NAS repeatedly corrupts

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Level 1

4 points

Time Machine backup on Synology NAS repeatedly corrupts

Dear all,

[Title is wrong IMHO but cannot be corrected. It should be more 'Time Machine backup on Synology NAS becomes repeatedly corrupted']

After several years of continuous and successfull backups using Time Machine on my Synology NAS, I got a message saying that my backup was no more usable (A "file System Dirty" was reported by fsck).

Having faced the same situation some years ago, I used the very same procedure as proposed by Garth Gillepsie (fsck -drfy ...) but to no avail. In some cases, I managed to repair the volume but it stays read-only and is not usable by TM.

I was ready to use Diskwarrior that helped me in some cases but thing is that the tool has been discontinued and my version is no more usable.

What is strange is that I successfully recovered an old version of the same sparsebundle (Thanks to HyperBackup ion my Synology) and managed to use it with TM... until it becomes corrupted after a few hourly backups.

Yesterday, I run the fsck command on a corrupted version of the sparsebundle, and the volume was successfully repaired. I run the fsck again with the -p option only: nothing was reported. But when I run fsck again, with the -drfy options, then the sparsebundle was declared seriously damaged (** The volume could not be verified completely.

volume check failed with error 7 ).

I'm wondering why a repaired volume can suddenly become seriously corrupted with another run of fsck...

So, now, I think that it remains only one option: erase the sparsebundle and restart a full backup.

Unless somebody has a better idea...

iMac 27″

Posted on Aug 10, 2026 11:48 PM

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Answer 1

pati31 Author

Level 1

4 points

Aug 12, 2026 2:48 AM in response to pati31

A quick update on this.

As I said, and following the advices from WheelieNick, I checked and reset my network configuration.

Then, I asked TM to restart the backup from scratch and since then, I did not see any corrupted backup reported by TM.

So, either I solved the problem with the checks and reset of my conf, or the previous sparsebundle was a bit too big and resulted in a corrupted file system.

Time will tell...

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Answer 2

WheelieNick

Level 8

49,065 points

Aug 11, 2026 3:57 AM in response to pati31

Your repeated Time Machine corruption on a Synology NAS points to underlying hardware, network, or file system instability. Since a restored backup corrupts again after a few hours, the root cause is active. Restarting a full backup will likely fail again soon without fixing this underlying problem first.

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Answer 3

pati31 Author

Level 1

4 points

Aug 11, 2026 6:18 AM in response to pati31

Last tentative performed this morning: I entirely deleted the old Backup bundle and restored it using the backups performed by HyperBackup.

Same results: after 3 backups successfully performed by TM, the message came back again and this time I decided to follow the advice of not trying to repair the bundle but to fully recreate a backup and losing the entire history.

Once again the backup was declared corrupted (QUICKCHECK ONLY; FILESYSTEM DIRTY).

I still do not have any clear explanation....

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Answer 4

pati31 Author

Level 1

4 points

Aug 11, 2026 6:20 AM in response to WheelieNick

Thanks for this. I launched a full backup few minutes ago and will see if the problem is still there. In the meantime, I will investigate around the network by restarting the switches, checking the cables and looking at the connections.

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